Microwave composite dielectric material with low loss and stable temperature as well as preparation method and application of microwave composite dielectric material

Abstract

The invention provides a low-loss temperature-stable microwave composite dielectric material and a preparation method and application thereof. The preparation method comprises the following steps: firstly, uniformly mixing strontium titanate, barium titanate or calcium titanate ceramic particles into polymer resin through ultrasonic and high-speed mechanical stirring treatment to obtain a mixed solution, performing composite molding on a three-dimensional woven spacer fabric serving as a reinforcement and the polymer resin mixed solution, and adjusting the temperature coefficient of resonance frequency of the three-dimensional woven spacer fabric. Therefore, the microwave composite dielectric material with low loss and stable temperature is obtained. The microwave composite dielectric material prepared by the invention has high hollowness, can effectively reduce dielectric loss of the structure, realizes low density, low dielectric constant, low dielectric loss and low resonant frequency temperature coefficient, and can be widely used for manufacturing microwave devices such as resonators, antennas, filters and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave dielectric materials, and in particular to a low-loss, temperature-stable microwave composite dielectric material and a preparation method and application thereof. Background Art

[0002] Microwave dielectric materials are widely used in filters, resonators and microwave dielectric substrates. As communication technology develops towards high frequency and high speed, microwave dielectric materials are required to have a low dielectric constant ( ) ensures the signal transmission rate, low resonant frequency temperature coefficient ( ) to reduce or control the temperature-induced changes in the dielectric properties of the circuit operating characteristics and ensure the frequency stability of the device during operation. Therefore, microwave dielectric materials with low dielectric constant, low dielectric loss and high temperature stability have been a research hotspot in recent years. However, when the dielectric constant is reduced, the resonant frequency temperature coefficient is difficult to approach zero.

[0003] Microwave dielectric ceramics are ideal microwave dielectric materials due to the designability of their resonant frequency temperature coefficients and the diversity of their dielectric constants. In recent years, researchers have achieved microwave dielectric materials with low resonant frequency temperature coefficients by adding a variety of ceramic materials with opposite resonant frequency temperature coefficients. However, the high dielectric constant of ceramics causes low signal transmission rates, high brittleness, low dielectric breakdown strength, and more stringent processing conditions, which hinders its application adaptability. Ceramic-polymer composites prepared by combining microwave dielectric ceramics with polymers can combine the advantages of both and regulate the dielectric properties of the composites. However, this method requires filling a large volume of ceramics, resulting in low strength, poor fluidity and flexibility in the composite material.

[0004] Therefore, microwave dielectric materials that can simultaneously meet the requirements of high strength, low dielectric constant, and low resonant frequency temperature coefficient still need to be developed. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a low-loss, temperature-stable microwave composite dielectric material and a preparation method and application thereof, which solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: According to a first aspect of the present invention, a method for preparing a low-loss, temperature-stable microwave composite dielectric material is provided, wherein a ceramic material is uniformly mixed into a polymer resin through ultrasonic and high-speed mechanical stirring treatment to obtain a mixed solution, and a three-dimensional woven spacer fabric is used as a reinforcement to perform composite molding with the polymer resin mixed solution to obtain the microwave composite dielectric material.

[0007] The existing microwave composite dielectric material fills ceramic material and short fiber into polymer. Although the preparation method is simple, the dielectric constant, dielectric loss and resonant frequency temperature of the obtained microwave composite dielectric material cannot meet the market requirements at the same time. The preparation method of the temperature-stable microwave composite dielectric material provided by the present invention firstly disperses the ceramic material evenly into the resin, and then evenly coats the mixed solution containing the ceramic material and the resin on the surface of the reinforcement fiber with a three-dimensional woven spacing structure. While the resin is solidified, it combines with the reinforcement fiber and wraps the reinforcement fiber. The added ceramic material is also evenly dispersed on the surface of the reinforcement fiber, reducing the local electric field concentration phenomenon, and thus the obtained microwave composite dielectric material is light in weight, low in dielectric constant, low in dielectric loss, and the resonant frequency temperature coefficient is close to zero.

[0008] Preferably, the three-dimensional woven spacer fabric is made of at least one of glass fiber, aramid fiber, polyethylene fiber, basalt fiber, polyphenylene sulfide fiber and polytetrafluoroethylene fiber.

[0009] Preferably, the ceramic material is selected from at least one of strontium titanate, barium titanate and calcium titanate.

[0010] Preferably, the polymer resin is selected from thermosetting resins or thermoplastic resins.

[0011] Specifically, the polymer resin is selected from at least one of epoxy resin, polyimide resin, phenolic resin, polytetrafluoroethylene resin, vinyl resin, polypropylene resin and the like.

[0012] Preferably, in the mixed solution, the ceramic material accounts for 5-15wt% of the mixed solution.

[0013] Preferably, the composite molding process is selected from resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM), or hand lay-up molding process.

[0014] According to a second aspect of the present invention, a low-loss, temperature-stable microwave composite dielectric material obtained by the above-mentioned preparation method is provided, wherein the resonant frequency temperature coefficient of the microwave composite dielectric material is -30ppm / °C~+30ppm / °C; the dielectric constant of the microwave composite dielectric material is 1.3~2, and the dielectric loss is ≤0.008.

[0015] Preferably, the tensile strength of the panel is 100-200 MPa, and the compressive strength is 4-10 MPa.

[0016] According to a third aspect of the present invention, there is provided an application of a low-loss and temperature-stable microwave composite dielectric material in filters, resonators and microwave dielectric substrates.

[0017] The present invention provides a low-loss, temperature-stable microwave composite dielectric material and a preparation method and application thereof. It has the following beneficial effects: This scheme provides a method for preparing a low-loss and temperature-stable microwave composite dielectric material. First, the ceramic material is evenly dispersed in the resin, and then the mixed solution containing the ceramic material and the resin is evenly coated on the surface of the three-dimensional woven spacer structure fabric with a hollow structure. While the resin is solidified, it combines with the reinforcement fiber and wraps the reinforcement fiber. The added ceramic material is also evenly dispersed on the surface of the reinforcement fiber. By adopting a three-dimensional woven spacer structure, the internal electric field distribution of the microwave composite dielectric material is optimized, the dielectric constant and dielectric loss of the overall material are reduced, and the ceramic material is introduced to regulate the dielectric temperature stability of the material as a whole. The low-loss and temperature-stable microwave composite dielectric material obtained can simultaneously meet the characteristics of light weight, low dielectric constant, low dielectric loss, and a resonant frequency temperature coefficient close to zero. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] The present invention discloses a method for preparing a low-loss temperature-stable microwave composite dielectric material, comprising the following steps: Step 1: First, prepare a three-dimensional woven spacer fabric with a hollow structure by three-dimensional weaving; Step 2, mixing the ceramic material and the polymer resin, and fully stirring them by ultrasonic and mechanical stirring to obtain a mixed solution containing the ceramic material and the resin; Step 3: Use hand lay-up molding, VARTM or RTM molding process to composite the reinforcement fiber and the mixed solution to obtain a microwave composite dielectric material with low loss and stable temperature.

[0020] The present application adopts a three-dimensional hollow structure composite material to eliminate most of the lossy materials while maintaining the integrity and mechanical properties of the material, effectively reducing the overall dielectric constant and dielectric loss of the material; ceramics have a large resonant frequency temperature coefficient, and ferroelectric phase ceramics are introduced into the material to make the material have the intrinsic dielectric response of ceramics, so the dielectric temperature stability of the entire material can be regulated, thereby obtaining a temperature-stable microwave composite dielectric material.

[0021] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0022] Example 1 (1) A three-dimensional woven spacer aramid fabric with a thickness of 6 mm was obtained by using 1500 denier aramid fiber through three-dimensional weaving technology as the reinforcing aramid fiber; (2) mixing strontium titanate ceramics with a particle size of 5 μm with polyimide resin, and fully stirring them by ultrasonic treatment and a high-speed stirrer to obtain a mixed solution in which the strontium titanate ceramics account for 10 wt% of the total content; (3) The mixed solution was evenly coated on the surface of the reinforcing aramid fiber by hand lay-up method, so that the mixed solution could fully penetrate into the interior of the fabric. The mixture was pre-cured at 160°C for 30 minutes, 260°C for 40 minutes, and 310°C for 40 minutes. During the curing process, an imidization reaction occurred to obtain a microwave composite dielectric material.

[0023] Example 2 (1) 300 tex glass fiber was used as the reinforcing glass fiber to obtain a 6 mm thick 3D woven spacer glass fabric through 3D weaving technology; (2) mixing strontium titanate ceramics with a particle size of 5 μm with epoxy resin, and fully stirring them by ultrasonic treatment and a high-speed stirrer to obtain a mixed solution in which the strontium titanate ceramics account for 10 wt% of the total content; (3) The mixed solution was filled into the reinforcing glass fiber by the VARTM molding process, the vacuum degree was controlled at -0.1 MPa, and the mixture was pre-cured at 50 °C for 3 h and cured at 70 °C for 7 h to obtain a microwave composite dielectric material.

[0024] Example 3 (1) 300tex basalt fiber was used as the reinforcement basalt fiber to obtain a woven spacer structure with a thickness of 6 mm through three-dimensional weaving technology; (2) Strontium titanate ceramics with a particle size of 5 μm are mixed with vinyl resin, a curing agent (methyl ethyl ketone) and a catalyst (cobalt isozincate), and the mixture is fully stirred by ultrasonic treatment and a high-speed stirrer to obtain a mixed solution in which the strontium titanate ceramics account for 15 wt% of the total content; (3) The mixed solution was filled into the reinforcing glass fiber through the VARTM molding process, the vacuum degree was controlled at -0.1 MPa, and it was completely cured at room temperature for 4 to 8 hours to obtain a ceramic-filled basalt fiber / vinyl resin temperature-stable microwave composite dielectric material.

[0025] Example 4 The preparation method of this embodiment is the same as that of embodiment 1, except that the strontium titanate ceramic accounts for 5 wt % of the mixed solution.

[0026] Example 5 The preparation method of this embodiment is the same as that of embodiment 1, except that the strontium titanate ceramic accounts for 15 wt % of the mixed solution.

[0027] Comparative Example 1 10wt% of strontium titanate ceramic, 15wt% of aramid fiber powder and 65wt% of epoxy resin and curing agent are fully mixed by ultrasonic treatment and high-speed mechanical stirring to obtain a mixed solution; the mixed solution is placed in a mold for pre-curing at 50°C for 2 hours, and then cured at 80°C for 6 hours to obtain a microwave dielectric composite material.

[0028] Comparative Example 2 The preparation method of this comparative example is the same as that of Example 1, except that in this comparative example, the strontium titanate ceramic accounts for 0wt% of the mixed solution.

[0029] Comparative Example 3 The preparation method of this comparative example is the same as that of Example 1, except that in this comparative example, strontium titanate ceramic accounts for 20wt% of the mixed solution.

[0030] The performance tests of the microwave dielectric composite materials prepared in Examples 1-5 and Comparative Examples 1-3 were respectively carried out, as shown in Table 1.

[0031] Table 1

[0032] By comparing Examples 1 to 3 with Comparative Example 1, it can be seen that by adding ceramic particles to the composite material, the resonant frequency temperature coefficient of the material can be regulated to achieve a microwave composite dielectric material with a low resonant frequency temperature coefficient, but the traditional solid structure has no obvious effect on the regulation of dielectric properties when the ceramic filling content is low. The resonant frequency temperature coefficient of the microwave dielectric material satisfies the mixing law, so the overall resonant frequency temperature coefficient can be regulated by adding materials with different resonant frequency temperature coefficients. The present invention combines a three-dimensional woven spacer structure composite material, and since most of the lossy and unstable dielectric properties are eliminated, a temperature-stable microwave composite dielectric material ( ), while ensuring that the composite material has low dielectric loss. In addition, the traditional method is to improve the mechanical properties of ceramic-polymer materials. The microwave dielectric composite material prepared by adding short fibers to ceramic-polymer resin has a tensile strength of up to 80MPa, but the effect of the short fibers on improving the mechanical properties of the composite material is not significant. The present invention combines the excellent mechanical and electrical comprehensive properties of fiber-reinforced composite materials with the dielectric properties regulation function of ceramic materials to achieve a high-strength ceramic-modified fiber-reinforced composite material.

[0033] From the comparison of Example 1, Examples 4-5 and Comparative Examples 2-3, it can be seen that when the strontium titanate ceramic filling content is between 5wt% and 15wt%, a microwave composite dielectric material with a low resonant frequency temperature coefficient can be achieved. Since ceramic particles are added to the resin matrix of the fiber-reinforced composite material, the composite material has the intrinsic dielectric response of strontium titanate ceramics, thereby regulating the dielectric performance stability of the composite material. When the strontium titanate content is 10 wt%, the resonant frequency temperature coefficient of the composite material is close to zero, has good temperature stability, and can be used in environments with extremely high requirements for temperature stability. When the strontium titanate content exceeds 10 wt%, the resonant frequency temperature coefficient of the composite material continues to increase in the positive direction. Therefore, by regulating the content of strontium titanate ceramics, the dielectric temperature stability of the entire composite material can be regulated, thereby preparing a temperature-stable microwave composite dielectric material.

[0034] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-loss temperature-stable microwave composite dielectric material, characterized in that: The ceramic material is uniformly mixed into the polymer resin by ultrasonic and high-speed mechanical stirring to obtain a mixed solution, and a three-dimensional woven spacer fabric is used as a reinforcement to perform composite molding with the polymer resin mixed solution to obtain the microwave composite dielectric material.

2. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The three-dimensional woven spacer fabric is made of at least one of glass fiber, aramid fiber, polyethylene fiber, basalt fiber, polyphenylene sulfide fiber and polytetrafluoroethylene fiber.

3. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The ceramic material is selected from at least one of strontium titanate, barium titanate and calcium titanate.

4. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The polymer resin is selected from thermosetting resins or thermoplastic resins.

5. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 4, characterized in that: The polymer resin is selected from at least one of epoxy resin, polyimide resin, phenolic resin, polytetrafluoroethylene resin, vinyl resin, polypropylene resin and the like.

6. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: In the mixed solution, the ceramic material accounts for 5-15wt% of the mixed solution.

7. The method for preparing a low-loss temperature-stable microwave composite dielectric material according to claim 1, characterized in that: The composite molding process is selected from one of resin transfer molding, vacuum assisted resin transfer molding, or hand lay-up molding processes.

8. A low-loss, temperature-stable microwave composite dielectric material obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The resonant frequency temperature coefficient of the microwave composite dielectric material is -30ppm / °C to +30ppm / °C; the dielectric constant of the microwave composite dielectric material is 1.3 to 2, and the dielectric loss is ≤0.

008.

9. The low-loss temperature-stable microwave composite dielectric material according to claim 8, characterized in that: The panel tensile strength of the temperature-stable microwave composite dielectric material is 100-200 MPa, and the flat compressive strength is 4-10 MPa.

10. Use of the low-loss temperature-stable microwave composite dielectric material according to claim 8 or 9 in filters, resonators and microwave dielectric substrates.

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